Apparatus and methods for lifting containers

Abstract

Apparatus for lifting an open top container, such as a drum, comprises a plurality of clamps each having shaped outer and inner jaws for frictionally gripping therebetween a corresponding sidewall portion of the container. A lifting mechanism closes the clamps and then lifts the container with the container suspended from the clamps. The apparatus is constructed so that the weight of the container increases the clamping pressure as the container is lifted. Other loads having an upright tubular sidewall can also be lifted. In one embodiment, the lifting mechanism employs wedges for closing the clamps, and in another embodiment the lifting mechanism employs linkages for closing the clamps.

What is claimed is:  
     
         1 . Apparatus for lifting a load having an upright tubular sidewall, comprising: 
 a plurality of clamps constructed and disposed to grip spaced sidewall portions, each of the clamps having cooperable, relatively movable outer and inner jaws shaped to conform to the shape of the respective sidewall portions, the outer jaws being disposed to engage outer surfaces of the respective sidewall portions and the inner jaws being disposed to engage inner surfaces of the respective sidewall portions; and    a lifting mechanism constructed to close the clamps to grip the respective sidewall portions frictionally and then to raise the lifting apparatus with the load suspended from the clamps.    
     
     
         2 . Apparatus according to    claim 1   , wherein the outer jaws are fixed to a frame, and the inner jaws are supported on the frame for movement relative to the outer jaws.  
     
     
         3 . Apparatus according to    claim 1   , wherein the clamps are constructed and disposed to grip opposite sidewall portions.  
     
     
         4 . Apparatus according to    claim 1   , wherein the lifting mechanism is operatively connected to the inner jaws and is constructed to move the inner jaws into engagement with inner surfaces of the sidewall portions.  
     
     
         5 . Apparatus according to    claim 1   , wherein the apparatus has elements that support the apparatus on a top edge of the sidewall when the apparatus is positioned relative to the load for lifting.  
     
     
         6 . Apparatus according to    claim 1   , wherein the lifting mechanism comprises a frame and a lifting member movable vertically relative to the frame, and the clamps are closed in response to upward movement of the lifting member relative to the frame.  
     
     
         7 . Apparatus according to    claim 6   , wherein the lifting mechanism includes linkages that connect the jaws of the clamps to the lifting member and that move to close the clamps when the lifting member is raised.  
     
     
         8 . Apparatus according to    claim 6   , wherein the lifting mechanism includes a pair of incline surfaces that move followers when the lifting member is raised, and thereby close the clamps.  
     
     
         9 . Apparatus according to    claim 8   , wherein the incline surfaces are part of wedge members mounted on the lifting member so as to move upwardly when the lifting member is raised, and the followers are mounted on pivot members pivotally supported on the frame, one of the jaws of each clamp being mounted on a respective pivot member and the other jaw of each clamp being fixed to the frame.  
     
     
         10 . Apparatus according to    claim 6   , wherein the inner jaws are mounted on pivot members that are pivotally supported on the frame, and wherein the lifting member has a pair of wedges mounted thereon adjacent to the respective pivot members, each pivot member having a follower thereon engaging an incline surface of a respective wedge so that when the wedges are moved upwardly by the lifting member, the upward movement of the wedges is converted to pivotal movement of the pivot members and the inner jaws are moved toward the outer jaws to close the clamps on the sidewall portions, and then continued upward movement of the lifting member lifts the load.  
     
     
         11 . Apparatus according to    claim 10   , wherein the wedges have guide surfaces, spaced from the incline surfaces and engaging guide members mounted on the frame for guiding movement of the wedges relative to the frame, and wherein the lifting member has additional guide surfaces engaging guide members mounted on the frame for guiding movement of the lifting member relative to the frame.  
     
     
         12 . Apparatus according to    claim 10   , wherein the frame comprises a pair of spaced plates and the lifting member comprises a plate disposed between the plates of the frame.  
     
     
         13 . Apparatus according to    claim 6   , wherein the inner jaws are mounted on first end portions of respective first links pivotally supported on the frame at intermediate regions of the first links, and wherein the lifting mechanism includes the first links and second links pivotally connected between respective second end portions of the first links and the lifting member.  
     
     
         14 . Apparatus according to    claim 13   , wherein the frame comprises a pair of parallel frame parts, each of the first links comprises a pair of parallel link parts disposed adjacent to respective frame parts, and each of the second links comprises a pair of parallel link parts disposed adjacent to respective first link parts.  
     
     
         15 . Apparatus according to    claim 13   , wherein the apparatus has a releasable latch for holding the links in positions that maintain the clamps open.  
     
     
         16 . Apparatus according to    claim 6   , wherein the apparatus has a releasable latch for holding the lifting member at a position relative to the frame at which the clamps are open.  
     
     
         17 . Apparatus according to    claim 16   , wherein the releasable latch comprises a pin insertable through corresponding holes in the lifting member and the frame.  
     
     
         18 . Apparatus according to    claim 1   , wherein jaws of the clamps have tapered lead-in portions to facilitate placement of the clamps over an upper edge of the sidewall portions.  
     
     
         19 . Apparatus according to    claim 1   , wherein the apparatus includes handles for manually positioning the apparatus relative to a container.  
     
     
         20 . A method of lifting a load having spaced sidewall portions, comprising: 
 disposing a plurality of clamps adjacent to respective sidewall portions, each clamp having cooperable, relatively movable outer and inner jaws shaped to conform to the shape of the respective sidewall portions, the outer jaws being disposed to engage outer surfaces of the respective sidewall portions and the inner jaws being disposed to engage inner surfaces of the respective sidewall portions;    moving the jaws of each clamp to close the clamps to grip respective sidewall portions frictionally; and    lifting the clamps so as to lift the load with the load suspended from the clamps.    
     
     
         21 . A method according to    claim 20   , further comprising increasing clamping pressure between the jaws of each clamp in response to lifting of the load.  
     
     
         22 . A method according to    claim 21   , wherein the increasing of the clamping pressure is due to a levering action that urges one of the jaws of each clamp toward the other jaw of each clamp.  
     
     
         23 . A method according to    claim 21   , wherein the increasing of the clamping pressure is due to a wedging action that urges one of the jaws of each clamp toward the other jaw of each clamp.  
     
     
         24 . A method according to    claim 21   , wherein the clamps are supported on a frame, and prior to closing the clamps on the respective sidewall portions the frame is supported on a top edge of the sidewall.  
     
     
         25 . Lifting apparatus comprising a plurality of gripping devices having shaped surfaces for gripping spaced sidewall portions of a container between the surfaces of each gripping device, the surfaces being shaped to conform to the shape of the spaced sidewall portions and being actuated by the weight of the container and/or its contents as the container is lifted to create a gripping force on the sidewall portions that allows the container and any contents to be lifted with the container suspended from the shaped surfaces.  
     
     
         26 . Lifting apparatus according to    claim 25   , wherein the gripping devices are actuated by mechanical advantage devices.  
     
     
         27 . Lifting apparatus according to    claim 25   , wherein the gripping devices are constructed to lift containers having straight sidewalls extending to a top edge of the sidewalls, the sidewalls being free of crimping, beading, or other surface formations that would aid in lifting of the containers.  
     
     
         28 . Lifting apparatus comprising clamp means including cooperable first and second jaws, a frame, and a lifting member movable relative to the frame, the first jaw being fixed to the frame and the second jaw being mounted on a pivot member pivotally supported on the frame, and incline surface means fixed to the lifting member, the pivot member having a follower that engages the incline surface means to move the second jaw toward the first jaw in response to movement of the lifting member relative to the frame.  
     
     
         29 . Lifting apparatus comprising a pair of spaced clamps, a frame, and a lifting member movable relative to the frame, each clamp having a first jaw fixed to the frame and a second jaw mounted on a pivot member pivotally supported on the frame, and a pair of incline surface members fixed to the lifting member, the pivot members having followers cooperable with the incline surface members, respectively, for moving the second jaws toward the first jaws when the lifting member is moved relative to the frame.  
     
     
         30 . Lifting apparatus comprising a frame, a pair of spaced clamps, each clamp having cooperable first and second jaws, a pair of linkages, and a lifting member movable relative to the frame, the first jaws being fixed to the frame, and the second jaws being fixed to first links of the linkages, respectively, the first links being pivotally mounted on the frame and being pivotally connected to second links of the linkages, respectively, that are pivotally connected to the lifting member, the linkages being constructed to move the second jaws toward the first jaws in response to movement of the lifting member relative to the frame.